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Old 06-14-2010, 08:02 PM   #1
spartanman OP
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Airhead rear main seal install: oil or no oil?

As I understand it, Part No. 11 11 1 261 739 is an upgraded rear main seal design. It looks remarkably different than the original spring-actuated lip seal. I've read it has a teflon sealing surface and therefore should be installed dry. This is consistent with my experience on Cummins 12V diesel engines that use teflon main seals front and rear. I've also read that the BMW seal should first be soaked in hot oil before installation. What's been your experience? Thanks.
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Old 06-14-2010, 08:15 PM   #2
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I've installed that teflon seal 10 times in as many years. I've never had one leak. I put mine in dry and dry. no soaking, no wetting.
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Old 06-14-2010, 08:46 PM   #3
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Dry.
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Old 06-14-2010, 09:05 PM   #4
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Matt Parkhouse did mine for me for while I watched (in my basement). He massaged it a bit (not sure why) and stuck it in there. Dry.

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Old 06-14-2010, 09:14 PM   #5
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The "massaging" is to shape the lip. This prevents the lip from tearing as the flywheel goes on.
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Old 06-14-2010, 10:11 PM   #6
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Easiest way is to install the seal on the "guide ring" for a couple hours. That lets the seal naturally conform to the shape when you install everything.

Also make REAL sure the seal goes in dry and straight (use a round disc with holes for the flywheel bolts) as a pusher. If you see some shavings on the side of the disk when you finish pushing it in flush, you increase the likely hood of a later leak.
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Old 06-15-2010, 04:51 AM   #7
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Dry it is. Thanks all for the help. Much appreciated. Beemerguru: I borrowed an installation tool like the one you describe. Seal went in clean and straight.
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Old 06-15-2010, 05:25 AM   #8
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Mostly good advice. The new seals are something like the 4th generation and do not need oil or forming. Put them in dry, square and to the right depth and you are in business.
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Old 06-15-2010, 06:23 AM   #9
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I did it dry. No leaks, no errors, and I have about 2K miles since the service.
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Old 06-15-2010, 06:42 AM   #10
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Quote:
Originally Posted by spartanman
As I understand it, Part No. 11 11 1 261 739 is an upgraded rear main seal design.
Hmm, isn't 11 11 1 338 342 the new one?
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Old 06-15-2010, 08:27 AM   #11
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Quote:
Originally Posted by AliBaba
Hmm, isn't 11 11 1 338 342 the new one?
Yes, this is the current part number.
When BMW changes part numbers (which happens a lot) it doesn't always mean the part itself has changed.
this the tool that I have been using. a pieces of nylon that I spun up in the lathe. That and a hammer and it's a snapperoo!

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wirewrkr screwed with this post 12-03-2010 at 11:17 PM
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Old 06-15-2010, 12:11 PM   #12
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so what happens if it goes in wet
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Old 06-15-2010, 07:47 PM   #13
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Quote:
Originally Posted by coastranger
so what happens if it goes in wet
Some say that is how they do it and it works fine.
I don't care to tempt fate when it comes down to having to do a job twice.
Whatever you want to do, do it.
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Old 06-16-2010, 07:50 AM   #14
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Quote:
Originally Posted by coastranger
so what happens if it goes in wet
It wouldn't hurt if if you smear alittle oil on the edges of the seal. It's going to see oil sooner or later.
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Old 06-16-2010, 07:57 AM   #15
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Not knowing any better at the time I put mine in wet. Seal is working fine with 2500 miles so far.
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